Short-wave apparatus



Aug. 12, 1947. H TUMCK 2,425,657

` sHoRT WAVE APPARATUS original Filed April 17, 1941 :5 sheets-sheet 1 L ,J INVENTOR l 4'5 4f/.wy 7am/cfr.

ATTORN EY Aug- 12, 1947. H.TUN1CK sHoRT'wAvE APPARATUS original Filed April 17, 1941 s sheets-sheet 2 N wf R O T N E V m ATTORNEY SHORT WAVE APPARATUS Original Filed April 17, 1941 3 Sheets-Sheet'3 I l I INVENTOR J 45'/ l Alf/efr 7E/Mcm ATTORNEY Patentecl Aug. 12, 1947 :SHORT-WAVE APPARATUS Harry Tuniek, Rye, N. Y., assignor to Radio Corporation of America, a corporation of Dela- Ware Original application April 17, 1941, Serial No.

388,999. Divided and this application December 13, 1943, Serial No. 514,021

17 Claims. l

This application is a division of my copending application Serial No. 388,999J filed April 17, 1941, now U. S. Patent #2,337,214.

My present invention relates to improvements in ultra short wave apparatus and particularly to apparatus useful for the production of frequency modulated waves. Generally, it is an object of my present invention'to provide improved apparatus for the eicient generation and frequency modulation of Waves of very short wave length.

In one form of my invention my improved apparatus comprises a space resonator having a gap. An electron discharge path is set up for providing a flow of electrons past the gap in such a Way as to cause the resonator to be excited at high frequency, To produce the electron ow, there is provided an electron emitting cathode which is grounded, an anode which is maintained at a negative potential `with respect to ground, and an intermediate electron permeable grid which is maintained at a positive potential With respect to ground. As will be explained more 'fully later, electrons oscillate through and about the ypositively charged grid and their simultaneouspassage across the gap excites the resonator. In order `to modulate the Waves so generated and set up in the resonator, signal voltages are applied `to the negatively charged anode. By `appropriate adjustment of these voltages, it Will be found that the arrangement will produce, over a useful range, linear frequency modulation substantially free of undesired amplitude modulation.

Various advantages, features and further objects of my invention will appear -as the more detailed description thereof proceeds.

In the drawings:

Figure 1 illustrates one form of my invention for producing very short frequency modulated waves. The system employs a cavity resonator excited by an electron stream, oneterminating electrode for which is varied in Voltage so as to produce the desired `frequency modulation.

Figure 2 is a modification in which an electron emitting surface has been used to replace the negatively charged anode of Figure 1;

Figure 3 illustrates diagrammatically still an-` other modication of my invention; and

Figure 4 is a modie'd form of Figure, 1.

Turning to Figure 1, I have provided a vacuum tube having an hermetically sealed, evacuated, cylindrical glass container 2. Within the tube 2 there is provided a cathode 4 at one base of `the tube, a disc-like plate 6 at the other base of the tube 2, and intermediate these two electrodes there is provided a perforated disc-like grid or control electrode 8. Grid 8 extends across the entire cross-section of tube 2. Cathode 4 is provided with a heater element l0 which may be energized by a suitable filament transformer I 2 whose primary is connected to any suitable source, not shown. The cathode 4, as shown, is connected directly to ground or may be maintained at a small negative potential with respect to ground by inserting a suitable biasing source in series with the ground lead I4. Similarly, the disc-like anode 6 may be connected to ground through a .variable source of potential I6 which, preferably, is adjusted so as to subject the anode 6 to a negative potential with respect to ground I 8. The grid 8 is connected by way of conductor 20 to potentiometer 22 in shunt to potential source 24 Tap 26 is so adjusted on potentiometer 22 as to cause the grid `8 to be subjected to a high positive potential.

As a consequence of the foregoing construction and connections, electrons are attracted from cathode 4 -by the positively charged grid 8 and are given such velocity that they pass through grid 8 only to approach the negatively charged anode -6 which now serves to slow up the electrons and repel them. In addition, after the electrons pass through the grid 8, the grid is now behind the electrons and tends to pull them back towards the cathode 4. It therefore follows that clouds of electrons are caused to oscillate through and about the grid 8.

By appropriately mounting a cavity resonator 28 about the tube 2, as shown, the pulses, clouds or groups of electrons oscillating between cathode 4 and anode 6 and through grid s inductively excite the resonator 28. By appropriate choice of voltages impressed upon the anode 6 and the grid 8 and by appropriately choosing the size of the gap 3U for the cavity resonator 28, as well as the dimensions of the cavity resonator 28, the electron cloud oscillations may be brought into synchronism with the resonant waves set up within the cavity oscillator, thereby producing oscillations of extremely high frequency and relatively high power. Output energy may be taken inductively from the cavity resonator by means of the metal loop or conductor 32 insulatingly passed through the walls of the cavity resonator 28. The latter is preferably made of a high conducting metal, such as copper, although it may also be made of Invar and coated on its interior surface with silver or copper. The cavity .resonator 28, together with the tube 2, may be placed within a temperature controlled container 34 provided with thermostatically operated heaters and fans so as to maintain the temperature of the system constant and thereby enhance frequency stability.

As a further method of frequency control, a loop 3B may be provided for picking up some of the energy within the cavity resonator and this high frequency energy may be frequency divided by a frequency divider 38 and fed to a detector 43. The detector 40 is also fed with constant frequency oscillations from a crystal controlled oscillator 42 which, preferably, is temperature controlled. If desired, of course, the output of the crystal oscillator may be frequency multiplied by a suitable frequency multiplier before being fed into the detector 40.

The beat frequency resulting from action of dector 40 upon the waves fed to it from oscillator 42 and divider 38 is fed to a coil 43 and .thence to a pair of off-tuned circuits 44, 4B having over-lapping resonance curves. The frequency discriminator system consisting of off-tuned circuits 44, 46 may also be mounted within a temperature controlled chambervli. The outputs of discriminator circuits 44, 46 are fed to detectors 50, 52 connected in opposition across resistor 54. When the system is operating at its proper frequency, there will be no Voltage drop across resistor 54. However, Y with departure in frequency of the oscillator from that for which the beat frequency from 40 lies at the cross-over point of the characteristics of circuits 44, 4S, a voltage drop will be established across resistance 54 and this voltage is fed through conductors 56 to a resistor 58 in series with the grid supply source 24. The voltage then injected into resistor 58 is of such sense and magnitude as to change the frequency of the oscillator in the direction tending to reduce the voltage drop across resistor 54.

The frequency controlling voltage may be fed, if desired, into the anode circuit by tapping conductors 56 to resistor 60. Such an arrangement is shown in Figure 4.

The output of the oscillator may be modulated by means of a voice microphone or other suitable pick-up device E4 whose output is amplified by amplifier 66. The output of 66 may be inserted in series with the resistor 68 in the grid lead 20 as illustrated in Figure 1 of my parent application, now U. S. Patent No. 2,337,214, or, as illustrated, the output of amplifier 65 may be fed to the plate 6 by connection of conductors 'l0 to resistance 60. By appropriately controlling the injected modulation voltages, the output of the oscillator will be frequency modulated and substantially free of amplitude modulation.

The oscillator of Figure 2 is similar in construction and operation to that shown in Figure 1 with the exception that the anode 6 has been replaced by a cathode l heated by heater 9 and energized by transformer Il. Variable negative voltages from sources i3 and I5 may be provided for subjecting the cathodes 4, 1 to initial negative potentials with respect to ground. Also in Figure 2 the inductance of the grid conductor 20 may be tuned out, at the operating frequency, by the series tuning condenser 22.

As shown diagrammatically in Figure 3 the grid may be made in the form of two perforated or Woven metal discs 3|, 33. The resonator may then occupy the position shown diagrammatically at 35.

In al1 of the modifications shown, the cavity resonator may be moved along the tube for D- timum operation. For example, it is not essential that the grid be symmetrically disposed with respect t0 the gap in the cavity resonator, but rather the entire resonator, if desired, may be arranged so that the gap is unsymmetrical to the grid or en- Ytirely to either side thereof Thus, for example, in

Figure 4 such an arrangement is shown where the grid 8 is located between the cathode 4 and gap 30.

Also, the cathodes may be in the form of electron guns producing a concentrated, thin cylindrical stream of electrons or, if desired, the cathodes may be of the type to provide the emission of a hollow cylinder of electrons, which cylinder is concentric with the tube 2 and the cavity resonator 28. Also, if desired, a variable unidirectional electro-magnet may be mounted outside of the cavity resonator and around the tube 2 to further control 'the cloud of electrons oscillating back and forth across the gap. Such an electro-magnetic system will, of course, serve to prevent diffusion of the pulses or groups or clouds of electrons swinging back and forth through the grid 8.

Incidentally, as illustrated in Figure 1, time constant condensers IDU may be provided so that the automatic frequency control operates only for slow drifts in frequency and does not wipe out the modulation frequency changes produced by the modulating system 64, 66.

The cavity resonators 28, shown in Figures l and 2, are preferably maintained at a small negative potential with respect to ground by means of source HD. This will serve to assist in the prevention of electron diffusion. However, the outer surface of the resonators may be connected directly to ground or, if desired, may be subjected to a positive D. C. potential with respect to ground, as shown in Figure 4.

In connection with Figures 1 and 4, bi-metallic strip lll4 closes when the temperature within the heat insulated chamber 34 becomes too high, thereby causing fan IDB to operate, in turn causing circulation of air around the oscillator and through openings in the chamber 34. When the temperature is too low, strip IGS closes, energizing heater III from source H2. A similar fan and heater system may be placed within chamber 48.

In order to expedite temperature control, metal ns may be added to the outer surfaces of the cavity resonators and/or small holes |20 may be provided in the walls of the cavity resonators so that air may circulate therethrough.

Having thus described my invention, what I claim is:

1. In combination, a space resonator having a gap, an electron discharge system for producing an electron ow across said gap, said system comprising an evacuated hermetically sealed container having therein an anode, a cathode and a grid, a circuit for heating said cathode, a connection for grounding said cathode, a connection for maintaining said grid at a positive potential with respect to ground, a circuit for maintaining said anode at a relatviely negative potential with respect to ground, a circuit for superimposing upon said anode voltage variations corresponding to a desired signal whereby frequency modulated waves are generated within said space resonator and a utilization circuit coupled to the space within the resonator for removing frequency modulated waves therefrom and enabling the utilization thereof.

2. Apparatus as claimed in claim 1, characterized by the vfact that said cathode is located to one side of said gap, said anode is located on the ausgew other side of said-garland said .-tgrid is :located to AVonesideofssaidgap.

3. lApparatus-'asclaimed in claim `1, `characterizedloy `the fact l that said i grid is Larranged `to one `side-of -saidgap and betweenisaidfgap and said cathode.

24. Incombination, arspace resonator having'a gap, a circuit for `subjecting said resonator vto a positivepotential .withrespect to..ground,ian elec- =tron *discharge system for `causing an electron Astream 4to 'now past said-gap,;said discharge vsysternV comprising augroundedfcathodefand Y anV anode 'subjected `to -a Vnegative 4unidirectional `potential with respect-to said cathode, acircuit Vfor varying the anode potentialin accordance .with modulating voltages ywhereby-the currents'ilowing in said :resonator are frequency modulated and a utilization circuit, coupledto thespacewithinlthe resonator, for vutilizing 'frequency vmodulated waves `setup-therein.

`5. In combination, a `space .resonator having a gap, an electron discharge system for producing anelectron Yflow past salid gap, said system comanode at a relatively negative potential with respect to ground, aA-circuit for maintaining said resonator at -a Apositive potential with respect to ground, and a circuitfor superimposing upon said anode, voltage variations corresponding to a desired signal whereby frequency modulated waves C are generated within said space resonator.

6. Apparatusas claimed in claim `5, characterized by the fact that said cathode is located to one side of said gap, said anode is located on 4the other side of said gap, vand vsaid grid Vislocated to .one sideofisaidgap,

"7. Apparatus as claimed in claim 5, characterized by the fact that said Ygrid is arranged tto ,one side of said gap and `betweensaid gap and said cathode.

8. `In combination7 a space resonator having a gap, an 4electrondischarge system for producing an electron Yi'loW across said igap, said system `comprising anevacuated,hermetically sealed container `having thereinanianodega cathodeJand a grid, a circuit Yfor heating vsaid fcathode, .a Aconnection for grounding said cathode, a connection ifor maintaining said grdai-a positive potential with respect .to ground, a circuit for maintaining said anode at a relatively negative potential with respect to ground, a circuit for superimposing upon said anode voltage variations corresponding to a desired signal whereby frequency modulated waves are generated Within said space resonator, and a utilization circuit coupled to the space Within the resonator for removing frequency modulated waves therefrom and enabling the utilization thereof, means for deriving from said resonator a portion of the waves generated therein, means for beating said derived waves with waves derived from a constant frequency generator to produce waves of intermediate frequency and means responsive to departures in frequency of said Waves of intermediate frequency from a predetermined value to produce a controlling voltage and means for impressing said controlling voltage upon the anode of said discharge syst-em to automatically frequency control the same.

9. Apparatus as claimed in claim 3 characterized by the fact that means are provided for fre- 6 Yquency fdividing said :portion of fwaves derived from'said resonatorffor'frequencycontrolling purposes :beforetheyare .beat with fthe fwaves derived from said constant frequency oscillation genera- -tor.

10. nicombination, fa-:space resonator having a gap, an electron-discharge system for producing .anelectron flow past saidegap, whereby'saidresfonator :is excited .fandcaused to .have high fre- =quency 1electricalWaves'set `,up therein, said dis- -charge system fincluding an electron emitting lcathode, an Tanode :and afgrid,.a circuit for heat- .ing #said cathode :to electron emitting condition, -a :circuit ffor subjecting rsaidxgrid to a positive potential with respect .to said cathode, a circuit ifor vmaintaining said anode at anegative `poten- Itial with .respecttofsaid cathode, circuitsfresponsive to'waves insaid `cavity for :producing a volt- =age which varies zinpolarityfandxmagnitude when Vthe frequency :of the Wavesinsaid -space resonaftor varies about a Vdesired operating frequency, and `a vcircuit for applying said voltage to said 'anode-'cathode :circuit for bringing the frequency of :thewaves 4set up in said cavity back to a desired Aoperating vfrequency.

Tl'l. Apparatus as :claimed fin claim 10, characterized by thefactxthata modulating circuit-is provided for additionally subjecting *said anode Ito cathode circuit :to :modulating voltages vwhere- :byfthe :waves :in said :cavity :are frequency .modulated rabout a desired mean frequency of operaltion.

1.2. vA :high frequency, frequency modulation vsystem :comprising a `space resonator `having a `gap,.fanfe'lectron discharge system `for producing l.an electron flow 4past l:said gap in such away as to set Lup high :frequency oscillations in said resonator, said discharge system comprising an electron :emitting cathode, a grid and an :anode arranged lin 'the order `named along `the axis of 4said gap, a 'circuit for subjecting said grid to 'a positive potential with respect to vsaid electron `:emitting cathode `a .circuit for subjecting said anode toa 'negativezpotential with respect to said electron :emitting cathode, 'instrumentalities utilizin'g aportion of the Waves set up in said reso- -naltor `for producing a voltage which -varies in polarity :and magnitude according to departures `in frequency-oflthewaves in said Aresonator' about -a desirecl'frequencyaof operation, means for applying said voltage to said anode and with `respect ftosaid Icathode in -suchra way as to maintain the Afrequency of foscillations generated within said `resonator atsubstantially a constant mean frefquency, Aandfrneans for `subjecting said anode to a variable modulating voltage with respect to said cathode so as to frequency modulate the waves within said cavity resonator, and an output circuit coupled to said cavity resonator for deriving frequency modulated Waves therefrom.

13. Apparatus for producing frequency modulated Waves comprising a metallic space resonator having a gap, an electron discharge system for producing oscillations of electrons past said gap, said discharge system comprising a grounded cathode, an anode, a circuit for subjecting said anode to a negative unidirectional potential with respect to ground, a grid at the side of the gap nearest the cathode, a circuit for subjecting said grid to a positive potential with respect to ground whereby electrons attracted from the cathode pass through said grid and oscillate across said gap, a circuit for varying the voltage of said anode in accordance with signal control potentials whereby the Wave energy set up within said space `7 resonator is frequency modulated, and a utilization circuit for deriving and utilizing frequency modulated waves from said metallic space resonator.

14. Apparatus for producing frequency modulated waves comprising a metallic space resonator having a gap, an electron discharge system for producing oscillations of electrons across said gap, said discharge system comprising agrounded cathode located on one side of said gap, an anode located on the opposite side of said gap, a circuit for subjecting said anode to a negative potential with respect to ground, a grid located adjacent the gap and at the side thereof nearest the cathode, a circuit for subjecting said grid to a positive potential with respect to ground whereby electrons pass through said grid and across said gap, and a circuit for Varying the voltage on the anode in accordance with signals whereby wave energy set up Within said metallic space resonator is frequency modulated, and a utilization circuit coupled to said resonator for deriving therefrom and utilizing frequency modulated waves set up within the space within the metallic resonator.

15. Apparatus for producing frequency modulated waves comprising a metallic toroidal space resonator having an annular gap at its inner periphery, an electron discharge system for producing oscillations of electrons across said gap, said discharge system comprising a cathode, a grid and an anode mounted within an evacuated space, the cathode and anode being located on opposite sides of the gap, the grid extending across the gap and lying in a plane to one side of said gap nearest the cathode, a direct current circuit connected between said cathode and ground, a direct current circuit connected between said anode and ground, said direct current circuits serving to maintain said anode at a negative potential with respect to said Cathode, a direct current circuit connected between said grid and cathode serving to maintain said grid at a positive potential with respect to said cathode, a source of modulating potentials, a circuit for injecting said modulating potentials in the circuit between said anode and cathode whereby frequency modulated waves are set up in said metallic space resonator which are substantially free of amplitude modulation, and an output circuit coupled to said space resonator for deriving therefrom frequency modulated waves.

16. Apparatus for producing frequency modulated waves comprising a metallic toroidal space resonator having an annual gap at its inner periphery, an electron discharge system for producing oscillations of electrons across said gap, said discharge system comprising a cathode, a grid and an anode mounted within an evacuated space, the cathode and anode being located on opposite sides of the gap, the grid extending across the gap and lying in a plane to one side of said gap nearest the cathode, a direct current circuit connected between said cathode and ground, a direct current circuit connected between said anode and ground, said direct currentl circuits serving to maintain said anode at a negative potential with respect to said cathode, a direct current circuit connected between said grid and cathode 'serving to maintain said grid at a positive potential with respect to said cathode, a detector, a circuit for feeding high frequency waves derived from said metallic Space resonator and from another circuit carrying high frequency waves to said detector in order to produce Waves of beat frequency in the output circuit of said detector, a discriminator-rectii'ler system coupled to the output circuit of said detector, said discriminatorrectifer circuit producing frequency controlling voltages, and a circuit for applying said frequency controlling voltages to the anode, cathode circuit of said electron discharge system.

17. Apparatus as claimed in claim 16 characterized by the fact that there is also inserted in said anode, cathode circuit modulating potentials whereby the waves generated in the space resonator are frequency modulated and substantially free of amplitude modulation.

HARRY TUNICK.

REFERENCES CITED The following references are of record in the le of this patent:

UNITED STATES PATENTS Number Name Date 2,337,214 Tunick Dec. 21, 1943 2,190,511 Cage Feb. 13, 1940 2,225,447 Haeff Dec. 17, 1940 2,278,210 Morton Mar, 31, 1942 2,227,372 Webster Dec. 31, 1940 1,873,842 Hyland Aug. 23, 1932 1,934,400 Bollman Nov. 7, 1933 1,988,609 Reeves Jan. 22, 1935 2,104,801 Hansell J an. 11, 1938 2,132,654 Smith Oct. 11, 1938 2,201,978 Bedford May 28, 1940 2,243,202 Fritz May 27, 1941 2,269,456 Hansen et al. Jan. 13, 1942 2,276,247 Hahn Mar. 10, 1942 2,250,104 Morrison July 22, 1941 

